Nitric oxide (.NO) potently modulates oxygen radical reactions and inflammatory signaling, yielding secondary oxides of nitrogen that display frequently-undefined reactivities and unique signaling properties. This project is designed to explore how NO-mediated oxidative reactions lead to the nitration of membrane and lipoprotein lipids. We propose to define in detail how .NO-derived reactive species induce nitration of polyunsaturated fatty acids and to identify the principal products of these reactions. We will then evaluate the biological formation, metabolism and unique signaling activities of these novel nitrated lipid mediators in models of tissue inflammatory injury. The proposed research plan utilizes a molecular and cellular framework for characterizing the chemical and biological properties of .NO-dependent fatty acid nitration products that in turn serves as a foundation for the testing of key concepts in model systems and human-derived tissues. The central hypothesis that underlies our research plan is that membrane and lipoprotein exposure to nitric oxide-derived inflammatory oxidants leads to the nitration of fatty acids to products that serve as signaling molecules. To test this hypothesis, the following Specific Aims will be pursued: #1. Explore the predominant mechanisms mediating lipid nitration in chemical reaction systems, lipoproteins and vascular cells; #2. Determine the structural and biological signaling properties of nitrated lipids; #3. Develop strategies for reliably detecting and quantifying nitrated lipids in models of inflammation and clinical specimens. The interaction of .NO and its products with hydrophobic tissue compartments is a critical element in the multifaceted contribution of .NO to cell signaling and tissue pathobiology. There, .NO and its products can undergo a rich spectrum of reactions with molecular oxygen, superoxide, peroxidases, transition metals, thiols, lipids and a variety of organic radicals to yield reactive species that serve to transduce .NO signaling, modulate tissue inflammatory responses and mediate the toxicological effects of xenobiotics. Upon successful completion of the proposed aims, detailed mechanistic information will be available regarding the formation, structure and signaling activities of lipid nitration products, and more will be known about the potential clinical diagnostic utility of these species as molecular "footprints" of oxidative inflammatory reactions.